I recently bought a bike for the first time in 10 years and after riding it for a couple of days the rear derailleur curled up like an insect ready to die. Is there any way I could fix that or am I gonna need a new shifter?
If the derailleur still shifts normally, you may have nothing to worry about. It sounds like it could be a few things:
Does your rear wheel sit in a dropout, or is the length of the wheelbase adjustable front to back? If it's adjustable, it's possible that the wheel skewer bolt got loose and allowed the rear wheel to slide forward, causing excessive slack in the chain.
Your chain somehow stretched dramatically
The spring in your derailleur is shot